The course of a patient who had diabetes mellitus occurring with acromegaly is followed before, during and after the development of pituitary apoplexy. Described herein are the acute reductions in plasma growth hormone, plasma cortisol and serum thyroxine concentrations, and alterations in posterior pituitary function subsequent to the apoplexy. Following the apoplexy, there was a complete regression of clinical diabetes accompanied by a return of normal insulin sensitivity and normal plasma insulin responses to pancreatic beta cell stimuli. The sequential changes in carbohydrate and insulin metabolism following pituitary apoplexy are discussed. The 25 previous cases of pituitary apoplexy in acromegaly are reviewed.